The invention relates to a unit for obtaining and displaying fundus image that can display a pseudo three-dimensional fundus image by alternately displaying two or more fundus images wherein optical axes are slightly shifted, and especially relate to a unit for obtaining and displaying fundus image for properly designating a position of a CUP on the fundus image three-dimensionally displayed.
When three-dimensionally watching the fundus image, a known unit for obtaining and displaying fundus image is conventionally used and in such a unit, two sheets of fundus images are obtained for the same eye to be examined from a point where optical axes of the eye to be examined and a fundus camera are slightly shifted, and a three-dimensional fundus image can be falsely displayed by alternately displaying these two fundus images (see Japanese patent application the publication number of which is 2003-24279). Then, observers, such as patients, examiners and doctors, feel a solidity in an explanation at the time of obtaining informed consent with a three-dimensional fundus image displayed in the unit for obtaining and displaying fundus image in comparison with an explanation with a normal two-dimensional image, and such an explanation with the three-dimensional image is extremely easy to be understood.
One of ophthalmic diseases is glaucoma. In glaucoma, optic nerve is destroyed and visual field is defective, so that glaucoma may cause loss of eyesight. A well-known method for testing glaucoma is to check a state of excavation of a disc, and in one of such methods, a C/D ratio (cup-to-disc ratio) is an index (see Japanese patent application publication number of which is H11-151206).
In order to compute a C/D ratio, it is necessary to measure an outer periphery of a cup and a diameter of an outer periphery of a disc from the fundus image.
When determining outer peripheries of a cup and a disc while watching the fundus image, the outer periphery of the disc is relatively easily determined even on the normal two-dimensional image since a difference between its periphery and its luminance is large, but the outer periphery of the cup is not easily determined from the normal two-dimensional image since a dent portion is necessary to be seen through. Therefore, an error of the C/D ratio may be large between the examiners, and diagnosis results of glaucoma may be different between the examiners thereby.
In order to solve such a problem, such a method is considered that a pseudo three-dimensional image is displayed by making use of technique of Japanese patent application publication No. 2003-24279 in order to determine the outer periphery of the cup on the image.
In a case where a position of a CUP is designated on a plurality of fundus images that are alternately displayed by such kind of the unit of obtaining and displaying fundus image, a designation subject is on different points on a plurality of fundus images and movements occur. If such a movement is large, it is difficult to designate. This is because the fundus images where optical axes of the fundus camera are slightly shifted are alternately displayed in order to falsely three-dimensionally display the fundus image. Even if the movement is small, the examiner does not know which point should be designated on the alternately displayed fundus images where the optical axes are shifted and is confused, and hesitates to designate the position.
Then, an object of the invention is to provide a unit for obtaining and displaying fundus image for properly designating a specific position on an image, displaying a three-dimensional image, as well as for displaying a three-dimensional pseudo fundus image by alternately displaying a plurality of fundus images wherein optical axes are slightly shifted.